1. Field of Invention
This application relates to the production of United States Pharmacopeia (U.S.P.) Water for Injection (WFI) and, more specifically, to the production of Water for Injection using reverse osmosis.
2. Discussion of Related Art
Water for Injection (WFI) is purified water used in formulation of a product that may be administered parenterally to a patient. This highly purified pharmaceutical grade of water is subject to a number of requirements regarding purity and sterility. Under current U.S.P. regulations, WFI can be produced through either distillation or reverse osmosis (RO) treatment of a feed water that itself meets U.S.E.P.A. National Primary Drinking Water Regulations. While treatment by RO is allowed under the regulations, it is not typically used in practice due to a number of drawbacks, including the possibility of downstream microbial growth (despite periodic sanitization) and the possible leaching of organic components from the RO membrane and other synthetic materials that form the RO cartridge.
U.S.P. requirements for WFI include a conductivity of less than 1.3 μS/cm at 25° C. Total organic carbon (TOC) is required to be below a level of 500 ppb, measured as carbon, and bacterial endotoxins must not exceed more than 0.25 U.S.P. endotoxin unit (EU) per milliliter. Thus, not only should bacteria be excluded, but bacterial endotoxins should also be excluded or otherwise controlled.
As a result of these impracticalities and others, the production of WFI by RO has not been widely practiced.